The present invention relates to a one component curing composition which is curable at room temperature or low temperatures by moisture, and more particularly to a one component curing composition containing a hydrolyzable silyl group-containing vinyl polymer which is hard to be subject to the influence of an undercoat and is particularly suitable for use in multicoat coating.
It is known that a silyl group-containing vinyl polymer having on the polymer chain end or the side chain thereof at least one silicon atom, to which a hydrolyzable group is linked, per one polymer molecule is curable by moisture, and is useful for providing a one component curing composition. A one component composition containing the hydrolyzable silyl group-containing vinyl polymer and a hardener or cure accelerating catalyst such as an organo tin compound, an amine compound or an acidic compound is curable at low temperatures by moisture in the atmosphere to form a network structure, thus forming a coating having excellent gloss, weathering resistance, discoloration resistance, solvent resistance, water resistance, heat resistance and hardness. It is possible to use the composition in various purposes, e.g. paint, adhesive, coating material and sealant, by utilizing the above excellent characteristics.
In the case of painting, multicoat coating is usually conducted by using various kinds of paints as an undercoat, an intermediate coat and a top coat. Therefore, it is important that a one component curing composition used as a paint has an excellent adhesive property to an undercoat or a top coat. Also, known one component curing compositions containing silyl group-containing vinyl polymers have the disadvantage. That is to say, in the case that a known urethane resin paint is first applied to form an undercoat (e.g. metallic base) and a one component curing composition, e.g. a coating composition containing a silyl group-containing vinyl polymer, a hardener such as dibutyl tin maleate and a solvent, is then applied to the undercoat, when it is necessary to conduct re-painting some minutes later to repair the paint film, the recoating of the coating composition causes the undercoat of the urethane resin paint to shrink and the appearance of the paint film is remarkably impaired. The initial repairability or recoatability in multicoat coating is very important in practical use.